Extensions of umbral calculus II: double delta operators, Leibniz extensions and Hattori-Stong theorems
We continue our programme of extending the Roman-Rota umbral calculus to the setting of delta operators over a graded ring with a view to applications in algebraic topology and the theory of formal group laws. We concentrate on the situation where is free of additive torsion, in which context the central issues are number- theoretic questions of divisibility. We study polynomial algebras which admit the action of two delta operators linked by an invertible power series, and make related constructions...